Displays utilizing organic light-emitting devices (OLEDs) such as organic light emitting diodes have shown great promise as thinner, lighter-weight displays than current liquid crystal displays (LCDs). An OLED is a device that utilizes an organic species (either a small molecule or a polymer) to emit light under an applied electric field. OLEDs are made out of one or more layers of organic materials stacked between conducting electrodes. A flow of electric current through this stack of materials stimulates the emission of light by the organic materials.
OLED technology is considered superior to LCD technology for use in displays for various reasons. For example, an OLED is an emissive system, creating its own light rather than relying on modulating a backlight. This leads to higher contrast, truer colors, crisper motion, and potentially lower power consumption compared to LCDs. Additionally, OLED displays may be manufactured via simpler and less expensive manufacturing processes than LCD displays.
However, current OLED displays suffer from short lifetimes, which may prevent the use of the OLEDs in such devices as computer monitors and large screen displays. The OLED displays must be encapsulated to prevent degradation of the organic layers caused by exposure to moisture and oxygen. Thin films of organic polymers and inorganic materials deposited over the OLEDs have been found to lessen damage to the OLED materials caused by such oxidants as moisture and oxygen. Such encapsulation layers are generally only needed over the active (light-emitting) portions of the displays, and not over other device regions, such as areas of the substrate intended for use as electrical contacts for connecting the device to external circuitry. However, the deposition of the encapsulation layers generally results in the uniform deposition of material over the entire substrate surface. Therefore, patterning and etching steps may be required to remove the encapsulant layers from contact areas and other such portions of the substrate.
Shadow masking may be used in certain evaporation-type deposition processes to achieve selective deposition or patterned deposition of the evaporated material while avoiding lithographic and/or etching steps. However, shadow masking may not be suitable for use with the vapor-phase deposition of some organic encapsulant materials, which may diffuse into the spaces between the shadow mask and the substrate.